I am trying to get all the trophies and I think I may have missed the trophy that requires you to get 11 vampire perks (forgotten the name of the trophy).

I have completed the dawnquard quest line and cured serana, so I am just wandering if there is another way to become a vampire lord or will I need to load another save?

Thanks

Serana and Harkon are the only ones who can turn you into a VL unless you have a mod to bypass that. If all you want is the trophy, you could just make a new character, start the Dawnguard questline as soon as you get out of Helgen, accept Harkon's offer and max out VL right away. The trophy will be on your account regardless of which character unlocked it, even if you delete them immediately afterwards.